The present invention relates to a hydraulic installation which comprises a mixing device having an inlet connection for receiving a flow of supply of cold water, an inlet connection for receiving a flow of supply of hot water, and a delivery connection for delivering mixed water. In particular, this invention relates to a new use of a known device called xe2x80x9cflow rate regulatorxe2x80x9d in connection with a mixing device to perform a function different from the functions for which this known device has been employed so far.
xe2x80x9cFlow rate regulatorsxe2x80x9d are currently commercially available and are known, for example, in a simple form from catalog 133/16/99 of the Dieter Wildfang GmbH of Mxc3xcllheim (Germany), and in a form combined with a nonreturn valve from German Patent No. 196 03 393. The basic feature of this device consists in the fact that, when inserted in a water pipeline, it permits a flow of water with a substantially constant flow rate that is preset upon the variationxe2x80x94within certain although wide limits, for example, from 1 to 10 barxe2x80x94of the pressure at which the water is supplied to the device. This device, therefore, represents a variable resistance to the flow, in other words, it opposes a resistance to the flow which, starting with a certain value of a given supply pressure, keeps diminishing strongly with the decrease of the water supply pressure. The substantially constant flow rate, which the flow rate regulator allows to pass, depends on the design features of the device.
The flow rate regulator is currently employed, in particular:
in order to make sufficiently constant the flow that runs through an instantaneously boiler, which would not work regularly if the flow running through it were not comprised between certain limits;
to limit the flow rate drawn from a shower, as prescribed in certain regulations; and
to limit the flow rate drawn from a faucet for the purpose of saving water.
The phenomenon with respect to which the invention proposes the employment of a flow rate regulator, in particular, involves the phenomenon of the temperature peak presented by the thermostatic mixing devices when there is a noteworthy and abrupt variation in the water supply pressure to one of the hot-and-cold water increments, a variation which, in most cases, involves an abrupt reduction of the cold water pressure because, from the water supply network, there is drawn a strong flow rate by an apparatus that entails high absorption such as a flowmeter flushing water device. The development of the phenomenon involved will be described with reference to this most frequent case.
When the pressure of the cold water supplied to a thermostatic mixing device diminishes abruptly, while the hot water supply pressure remains constant or almost constant, then the incoming cold water flow will diminish correspondingly, and, therefore, the temperature of the mixed water goes up abruptly. The temperature of the mixed water is detected by a thermometric element which, in the presence of a temperature increase, activates a regulating mechanism that provides for choking a passage for the hot water so as to return to the correct value imposed by the temperature of the mixed water. However, this regulating action involves a certain hysteresis due to the fact that regulation requires a certain period of time to be performed. During the period of transition in which takes place the regulating action as such, the temperature of the mixed water that is drawn presents an initial peak indicating a temperature rise, which can involve several degrees and which is then gradually attenuated until the prescribed temperature is once again reached. This temperature rise peak is extremely disturbing to the user, for example, during a shower, and it attains particularly high values, which can even turn out to be dangerous.
The same phenomenon could happen if, in a somewhat special case, there were to be an abrupt increase in the hot water supply pressure. Instead, a similar phenomenon, but with a temperature peak decline, occurs when it is the hot water supply pressure that drops abruptly or when the cold water supply pressure rises abruptly.
Similar phenomena not in the form of temperature peaks but in the form of variations in the temperature of the water that is drawn occur under similar conditions even in nonthermostatic mixing devices.
The inconveniences connected with this phenomenon can be partly remedied by installing in water supply pipelines up the line from the thermostatic mixing device a pressure compensator. However, this expensive additional device increases the size and complexity of the installation also because it must be connected to both of the cold water and hot water supply pipelines; that raises the cost of the equipment and of the operations involved in its installation; besides, this is a delicate operation; it is easily subject to failure, especially due to deposits, and it requires a certain amount of maintenance. By the way, it does not operate in an entirely satisfactory manner because, when the pressure is reduced in a pipeline, the compensator provides for the reduction of the passage offered to the other pipeline and thus corrects the mixing ratio but modifies the flow rate that is drawn. On the other hand, the operation of the pressure compensator can under certain conditions cause phenomena of instability.
As a matter of fact, the phenomenon described here is considerably toned down because, without using a pressure compensator proposed, for example, in Italian Patent Application No. TO 99 A 000 162, it involves introducing into one or both water supply connections of the thermostatic mixing device and particularly in the connection for the supply of cold water a choking member. This choking member has the effect of causing the regulating mechanism controlled by the thermometric element to be arranged normally in an asymmetrical position and, in particular, if the choking member is inserted in the cold water supply connection, it is arranged closer to the position in which the regulating mechanism actually chokes the passage of the hot water. Consequently, the regulating mechanism itself is more ready to react to a rise in the temperature of the mixed water and it is therefore capable of causing a more moderate temperature peak.
Further, document GB-A-2 303 685 discloses a mixer control comprising a mixing chamber at which thermostatically controlled valve means is provided for controlling mixture of hot and cold water for an adjustable discharged water temperature selectable by manual operation of the valve means, an outlet by way of which mixed water from the mixing chamber passes to be discharged from the mixer control, and a temperature responsive shut-off valve at the outlet which is normally open but which is operated automatically to close the outlet when the temperature of water from the mixing chamber exceeds a predetermined value which will normally be at or just above the maximum permitted operating temperature of the mixer control.
Although the shut-off valve according to this prior art provides a back-up for the thermostatically controlled valve means to cut-off water discharge should the valve means not respond, or not respond quickly enough, to an increase in the discharged water temperature to an undesirable level, a disadvantage of this prior art consists in the fact that the shut-off valve considerably adds to the structural complexity and cost of the known mixer control.
In addition, document GB-A-2 303 685 generally discloses that xe2x80x9cflow regulatorsxe2x80x9d may be included at the hot and cold inlets to optimise performance of the mixer control in high or uneven inlet water pressure conditions. The structure and the function of these xe2x80x9cflow regulatorsxe2x80x9d however are not described in more detail.
The object of the present invention is to provide a hydraulic installation in which undesirable temperature increases as described above are reduced or eliminated at low effort and cost.
According to the present invention a hydraulic installation is provided which comprises a mixing device having an inlet connection for receiving a flow of supply of cold water, an inlet connection for receiving a flow of supply of hot water, and a delivery connection for delivering mixed water, and which further comprises a flow rate regulating device inserted in the passage of at least one of the flows of supply of cold water and hot water directed to the mixing device, wherein the flow rate regulating device is adapted to permit, within certain limits of the pressure at which the water is supplied to the flow rate regulating device, the passage of a flow of water having a predetermined and substantially constant flow rates, thus reducing the temperature peal presented by the mixed water drawn from the mixing device when the pressure of the water supplied to one of the inlet connections varies abruptly with respect to the pressure of the water supplied to the other inlet connection.
Research conducted by the inventor showed that extremely more satisfactory results are obtained if, in place of a standard choking member as disclosed in Italian Patent Application No. TO 99 A 000 162, constituting a resistance with an unchangeable value, one installs a flow rate regulating device at least in one water supply connection and preferably in the water supply connection for the cold water or possibly in both water supply connections.
The reason for the significant improvement in the performance of the thermostatic mixing device resides in the fact that, when the pressure in a water supply connection in which is installed a flow rate regulator drops abruptly, the resistance opposed to the flow of the flow rate regulator also drops immediately and, therefore, the initial variation of the temperature of the mixed water, which gives rise to the regulating action of the thermometric element, is for this reason alone much more reduced than what would be the case if the flow rate regulator were not installed. On the other hand, the flow rate regulator by itself constitutes a choking member and therefore offers the above-mentioned advantage of speeding up the regulating action when compared to what it would be if such a choking member were not there. The coexistence and the synergism of these two actions give rise to significant constant advantages. An important factor in this action is represented by the fact that the reaction of the flow rate regulator is extremely fast and practically instantaneous. It follows from this that a thermostatic mixing device which, in the absence of the proposed provision, would have given rise to a temperature rise peak of several degrees, instead leads to a significantly reduced temperature peak, for example, amounting to xc2xd a degree, which does not cause any inconvenience and may even pass unnoticed.
Naturally, the flow rate regulator installed in at least one water supply connection of the thermostatic mixing device can be of the type combined with a nonreturn value in all cases where the presence of such a valve is desirable.